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06 October 2013

Earthquake gives birth to brand new island off Pakistan coast

Satellite
view of the new island raised from the sea bed near the city of
Gwardar, Pakistan in the wake of the recent earthquake. Image at right
shows the scene in April before the island’s creation. Click to enlarge.
Credit: NASA

On September 24 a major earthquake rocked western Pakistan killing at
least 515 people and leaving more than 100,000 homeless. While the
death and devastation caused by the 7.7 magnitude temblor makes the mind
and heart reel, amid the chaos a new island was born. Its muddy top
surfaced offshore in West Bay near Gwadar, Pakistan some 230 miles (370 km) from the epicenter.

Great little video of local people exploring the newly-birthed island
Two days later on Sept. 26, the advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite took the picture above of the newly exposed sea bottom located 0.6 miles (1 km) from shore.
“The island is really just a big pile of mud from the seafloor that
got pushed up,” said Bill Barnhart, a geologist at the U.S. Geological
Survey who studies earthquakes in Pakistan and Iran.

Aerial
view of the new island off the southern coast of Pakistan in the
Arabian Sea. It’s 250-300 feet
across and 60-70 feet high. Boaters are
anchored off the island at upper right.
Credit: National Institute of
Oceanography

The island, seen closeup in the aerial view, extends 250 to 300 feet
(75-90 meters) across and stands 60 to 70 feet (15-20 meters) above the
water line. The surface is a mixture of mud, fine sand, and solid rock.
In the video, you’ll see people already treading on what a day before
had been the bottom of the sea.

Earth’s
crust or lithosphere is broken up into distinct plates of lighter rock
rafting atop the denser, slightly viscous rocks of the upper mantle.
There are 8 major plates and many minor ones. The island is near the
active boundary of the Arabian and Eurasian plates. Credit: Wikipedia

Small, short-lived islands are fairly common in this part of the
world. As the Arabian continental plate dives beneath the Eurasian
crustal plate, accumulated mud (sediments) are scraped off and deposited
as temporary islands. Earthquakes can create new islands, too. When a
shallow pockets of gas like methane or carbon dioxide get trapped under
pressure by layers of muddy sediments, powerful seismic waves can
trigger their sudden release.
“When that layer becomes disturbed by seismic waves (like an
earthquake), the gases and fluids become buoyant and rush to the
surface, bringing the rock and mud with them,” said Barnhart.
Watch out! Highly-flammable methane still vents from the brand new
island. When I saw someone setting it afire in the video, it made me
wonder how we’ve managed survived so long on this planet without blowing
ourselves up.
Like the fate of many islands before it, this one will likely
disappear. Underground gas will cool and compress or simply escape,
allowing the raised crust to sink back down into the sea bottom. Waves
and weather will nibble the island to pieces, returning it back to the
sea in a matter of months.